The present invention relates to a food frying apparatus or utensil, particularly for use in a large size kitchen, such as a commercial kitchen. The present invention particularly is directed to such an apparatus which is of the type having an electric heater for the indirect heating of the frying oil or fat.
Traditionally, an electric frying apparatus has included a vessel, for example formed of stainless steel, a rear portion of which has at least one armored resistance heater hingedly mounted or guided in a manner such that during operation its active heater portion is completely immersed in the frying oil. In this manner, there is achieved direct heating of the oil. However, due to the low heat transmission coefficient between the surface of the heater and the oil, there occurs a substantial temperature difference of as much as 100.degree. C. or more between the heater surface and the oil. As a result, the oil in contact with the heater surface is subjected to a great amount of heat and therefore is subjected to degradation which, in addition to rendering cleaning of the resistance heater difficult, converts some of the oil to substances which constitute particular health hazards.
One attempt to solve such problems of a conventional electric frying apparatus has involved increasing the heat transmitting surface area of the resistance heater in proportion to its capacity, thereby to attempt to reduce the temperature difference between the heater surface and the oil to more acceptable values. This solution however requires the employment of a resistance heater having excessive dimensions and intricate shapes. This complicates the design, use and, above all, the frequency and difficulty of periodic cleaning of the apparatus.
A further attempt to solve the above problems has involved inserting an agitator into the oil, thereby to reduce such temperature and to prevent the excessive heating of the oil when in direct contact with the heater surface. This solution however only complicates the construction of the apparatus without eliminating the difficulties with regard to cleaning, since the resistance heater always is immersed in the oil during use of the apparatus.
Recently, it has been proposed to eliminate the above traditional difficulties by providing for indirect heating of the oil. In this arrangement, the oil is heated in a separate container which communicates with the vessel of the frying apparatus. There is provided means for forcibly circulating the oil between the vessel and the container. Electrical resistance heaters are wound onto the outer wall surface of the container in intimate contact therewith, for example by being welded or soldered thereto. This solution is advantageous in that it reduces certain of the shortcomings of frying apparatus provided with direct heating, due to the strong turbulence occurring in the heat exchange zone and resulting in a reduction of the temperature difference between the oil and the heating surface. On the other hand, attempts at this solution have resulted in certain other structural and functional difficulties. Specifically, the heating container is usually disposed vertically and therefore is required to have a substantial axial length, thus occupying a considerable vertical space below the bottom of the vessel. Additionally, the container has to be provided with an element mounted within the container for agitating and circulating the oil, and such element has to be driven by an externally mounted motor. To avoid problems with regard to sealing of a rotating shaft extending into the container, the motor is mounted above the level of the oil in the frying vessel. However, as a practical matter such motor location is not readily accessible and causes design and operating problems. Yet further, it is necessary to attempt to provide optimum conditions and ease for cleaning the container and particularly the circulating means. This however is practically not possible with the motor mounted at an elevated position.